Interest in the field of functionalized polymeric materials stems from the desire to combine the unique properties of a functional group with those of a high molecular weight polymer.
Functionalized polymers have the potential for crosslinking via ionic interactions and covalent bonds, leading to improved properties for applications such as polymer blends. The introduction of specifically interacting groups is a particularly versatile route to miscibility enhancement. Other applications of these materials are in membranes, packaging, dispersants, adhesives and coatings. In addition, functionalized polymers may be used in the modification of existing materials to alter their adhesion, processability, solubility, dyeability, thermal, mechanical, and other properties.
Functional groups can be introduced into a polymer by two general approaches: (1) chemical modification of a nonfunctionalized, preformed polymer, or (2) polymerization or copolymerization of monomers containing the functionality. The second method has the advantages of producing a more homogeneous polymer with more uniform functionalization, the ability to analyze the monomers prior to polymerization, and the ability to control loading and distribution of functional groups along the polymer backbone.
Various different functional or other polar groups have been incorporated into a number of polyolefin and polyvinyl materials. Successful functionalization is typically performed after polymer formation. In many instances, only terminal functionalization is achieved. Where functionalized monomers have been polymerized to prepare functional group-bearing polymers, the extra steps of masking the monomer functionality prior to polymerization, and then subsequently removing the mask, have been required. Limited success has previously been achieved in the polymerization of functionalized diene monomers, although such monomers have enormous commercial significance and utility in materials such as elastomers, adhesives, molded mechanical articles, and the like.
Initial work with nonsilicon-containing functionalized dienes was reported by Petzhold et al., which focused on anionic polymerization of N,N-diethylaminoisoprene and elucidation of microstructures. Petzhold, C., et al., Makromol. Chem., Rapid Commun., 14, 33-43 (1993), refers to low yields (&lt;50%) of low molecular weight (number-average molecular weight 5000) polymers obtained by anionic and radical polymerization of N,N-diisopropyl-2-vinylallylamine. Petzhold, C., et al. Marcomolecules, 27, 3707-13 (1994), refers to low yields of low molecular weight polymers obtained by anionic polymerization of a series of N,N-dialkyl-2-vinylallylamines.
What is needed are new functionalized diene monomers and methods for preparing and polymerizing functional dienes to produce high yields of functionalized diene polymers, without the requirements of masking and unmasking the functional group, or of adding the functionality only after polymerization.